What’s next? I sprayed with more PB Blaster in the meantime. I’m thinking a reverse drill bit and extractor is the next thing to try. Any other suggestions?
If you have the right sized reverse bit than try that first and if no luck try the extractor bits. A regular bit with extractors will also work fine. Let the PB Blaster do it's thing for at least a couple days if the drill/extractors don't work at first. If you happen to have a mini-butane torch try heating up just the bolt a little or a soldering iron on the bolt can help too.